Dns.BeginResolve(String, AsyncCallback, Object) Dns.BeginResolve(String, AsyncCallback, Object) Dns.BeginResolve(String, AsyncCallback, Object) Dns.BeginResolve(String, AsyncCallback, Object) Method

Definition

Warning

This API is now obsolete.

Begins an asynchronous request to resolve a DNS host name or IP address to an IPAddress instance.

public:
 static IAsyncResult ^ BeginResolve(System::String ^ hostName, AsyncCallback ^ requestCallback, System::Object ^ stateObject);
[System.Obsolete("Use BeginGetHostEntry instead")]
[System.Obsolete("BeginResolve is obsoleted for this type, please use BeginGetHostEntry instead. http://go.microsoft.com/fwlink/?linkid=14202")]
[System.Obsolete("BeginResolve is obsoleted for this type, please use BeginGetHostEntry instead. https://go.microsoft.com/fwlink/?linkid=14202")]
public static IAsyncResult BeginResolve (string hostName, AsyncCallback requestCallback, object stateObject);
static member BeginResolve : string * AsyncCallback * obj -> IAsyncResult
Public Shared Function BeginResolve (hostName As String, requestCallback As AsyncCallback, stateObject As Object) As IAsyncResult

Parameters

hostName
String String String String

The DNS name of the host.

requestCallback
AsyncCallback AsyncCallback AsyncCallback AsyncCallback

An AsyncCallback delegate that references the method to invoke when the operation is complete.

stateObject
Object Object Object Object

A user-defined object that contains information about the operation. This object is passed to the requestCallback delegate when the operation is complete.

Returns

An IAsyncResult instance that references the asynchronous request.

Exceptions

The caller does not have permission to access DNS information.

Examples

The following example uses BeginResolve to resolve a DNS host name to an IPAddress.

public ref class DnsBeginGetHostByName
{
public:
   static System::Threading::ManualResetEvent^ allDone = nullptr;
   ref class RequestState
   {
   public:
      IPHostEntry^ host;
      RequestState()
      {
         host = nullptr;
      }
   };

   static void RespCallback( IAsyncResult^ ar )
   {
      try
      {
         // Convert the IAsyncResult* Object* to a RequestState Object*.
         RequestState^ tempRequestState = dynamic_cast<RequestState^>(ar->AsyncState);
         
         // End the asynchronous request.
         tempRequestState->host = Dns::EndResolve( ar );
         allDone->Set();
      }
      catch ( ArgumentNullException^ e ) 
      {
         Console::WriteLine( "ArgumentNullException caught!!!" );
         Console::WriteLine( "Source : {0}", e->Source );
         Console::WriteLine( "Message : {0}", e->Message );
      }
      catch ( Exception^ e ) 
      {
         Console::WriteLine( "Exception caught!!!" );
         Console::WriteLine( "Source : {0}", e->Source );
         Console::WriteLine( "Message : {0}", e->Message );
      }
   }
};

int main()
{
   DnsBeginGetHostByName::allDone = gcnew ManualResetEvent( false );
   
   // Create an instance of the RequestState class.
   DnsBeginGetHostByName::RequestState^ myRequestState =
      gcnew DnsBeginGetHostByName::RequestState;
   
   // Begin an asynchronous request for information like host name, IP addresses, or
   // aliases for specified the specified URI.
   IAsyncResult^ asyncResult = Dns::BeginResolve( "www.contoso.com",
      gcnew AsyncCallback( DnsBeginGetHostByName::RespCallback ), myRequestState );
   
   // Wait until asynchronous call completes.
   DnsBeginGetHostByName::allDone->WaitOne();
   Console::WriteLine( "Host name : {0}", myRequestState->host->HostName );
   Console::WriteLine( "\nIP address list : " );
   for ( int index = 0; index < myRequestState->host->AddressList->Length; index++ )
      Console::WriteLine( myRequestState->host->AddressList[ index ] );
   Console::WriteLine( "\nAliases : " );
   for ( int index = 0; index < myRequestState->host->Aliases->Length; index++ )
      Console::WriteLine( myRequestState->host->Aliases[ index ] );
}
class DnsBeginGetHostByName
{   
   public static System.Threading.ManualResetEvent allDone = null;

   class RequestState
   {
      public IPHostEntry host;
      public RequestState()
      {
         host = null;
      }
   }

   public static void Main()
   {
     allDone = new ManualResetEvent(false);
     // Create an instance of the RequestState class.
     RequestState myRequestState = new RequestState();

     // Begin an asynchronous request for information like host name, IP addresses, or 
     // aliases for specified the specified URI.
     IAsyncResult asyncResult = Dns.BeginResolve("www.contoso.com", new AsyncCallback(RespCallback), myRequestState );

     // Wait until asynchronous call completes.
     allDone.WaitOne();
     Console.WriteLine("Host name : " + myRequestState.host.HostName);
     Console.WriteLine("\nIP address list : ");
     for(int index=0; index < myRequestState.host.AddressList.Length; index++)
     {
       Console.WriteLine(myRequestState.host.AddressList[index]);
     }      
     Console.WriteLine("\nAliases : ");
     for(int index=0; index < myRequestState.host.Aliases.Length; index++)
     {
       Console.WriteLine(myRequestState.host.Aliases[index]);
     }      
   }
   
   private static void RespCallback(IAsyncResult ar)
   {
     try 
     {
       // Convert the IAsyncResult object to a RequestState object.
       RequestState tempRequestState = (RequestState)ar.AsyncState;
       // End the asynchronous request.
       tempRequestState.host = Dns.EndResolve(ar);
       allDone.Set();
     }
	   catch(ArgumentNullException e) 
     {
       Console.WriteLine("ArgumentNullException caught!!!");
       Console.WriteLine("Source : " + e.Source);
       Console.WriteLine("Message : " + e.Message);
     }   
     catch(Exception e)
     {
       Console.WriteLine("Exception caught!!!");
       Console.WriteLine("Source : " + e.Source);
       Console.WriteLine("Message : " + e.Message);
     }
   }
}
Class DnsBeginGetHostByName
    
    Class RequestState
        Public host As IPHostEntry
        
        Public Sub New()
            host = Nothing
        End Sub 'New
    End Class 'RequestState
    
    
    Public Shared Sub Main()
     Try
        ' Create an instance of the RequestState class.
        Dim myRequestState As New RequestState()
        
        ' Begin an asynchronous request for information such as the host name, IP addresses, 
        ' or aliases for the specified URI.
        Dim asyncResult As IAsyncResult = CType(Dns.BeginResolve("www.contoso.com", AddressOf RespCallback, myRequestState),IAsyncResult)

        ' Wait until asynchronous call completes.
        While asyncResult.IsCompleted <> True
        End While
        
        Console.WriteLine(("Host name : " + myRequestState.host.HostName))
        Console.WriteLine(ControlChars.Cr + "IP address list : ")
        Dim index As Integer
        For index = 0 To myRequestState.host.AddressList.Length - 1
            Console.WriteLine(myRequestState.host.AddressList(index))
        Next index
        Console.WriteLine(ControlChars.Cr + "Aliases : ")

        For index = 0 To myRequestState.host.Aliases.Length - 1
            Console.WriteLine(myRequestState.host.Aliases(index))
        Next index
    catch e as Exception
            Console.WriteLine("Exception caught!!!")
            Console.WriteLine(("Source : " + e.Source))
            Console.WriteLine(("Message : " + e.Message))
    End Try
    End Sub 'Main
    
    
    Private Shared Sub RespCallback(ar As IAsyncResult)
        Try
            ' Convert the IAsyncResult object to a RequestState object.
            Dim tempRequestState As RequestState = CType(ar.AsyncState, RequestState)

            ' End the asynchronous request.
            tempRequestState.host = Dns.EndResolve(ar)
            Catch e As ArgumentNullException
            Console.WriteLine("ArgumentNullException caught!!!")
            Console.WriteLine(("Source : " + e.Source))
            Console.WriteLine(("Message : " + e.Message))
            Catch e As Exception
            Console.WriteLine("Exception caught!!!")
            Console.WriteLine(("Source : " + e.Source))
            Console.WriteLine(("Message : " + e.Message))
        End Try
    End Sub 'RespCallback

Remarks

The asynchronous BeginResolve operation must be completed by calling the EndResolve method. Typically, the method is invoked by the requestCallback delegate.

This method does not block until the operation is complete. To block until the operation is complete, use the Resolve method.

For more information about using the asynchronous programming model, see Calling Synchronous Methods Asynchronously.

Note

This member emits trace information when you enable network tracing in your application. For more information, see Network Tracing in the .NET Framework.

Security

DnsPermission
for accessing DNS information. Associated enumeration: Unrestricted

Applies to

See also